Genes: reasons why some men are just born to cheat.

‘It’s not you dear, it’s me: the genetic reasons why some men cheat’ – An Evaluation.

The problems in social representations of scientific theories are blindingly obvious. As audiences simply absorb, in an impoverished and lessened form, the information and ideas which stem from scientific research, as depicted on television or in newspapers, real knowledge is diluted, distilled, and yet is often accepted as truth by the general population. According to Massimiano Bucchi (1998) the media is a ‘dirty messenger’ for science wherein factual and scientific information is represented in a simpler, weaker or distorted way to a lay public who merely find science ‘too difficult’. The current article ‘It’s not you dear, it’s me: the genetic reason why some men are just born to cheat’ provides an excellent example of how knowledge is elaborated and manipulated at the popular level and given greater concreteness and relevance. This report will to some degree critically evaluate the above mentioned article as printed in The Times newspaper, September 2, 2008 issue, and will consider the conclusions reached by its author Mark Henderson, the Science Editor for the publication. Additionally, it will draw upon other existing sources in the literature in order to substantiate or falsify the claims made.

In evaluating a piece of journalistic writing such as the one presented by Henderson, it is crucial to consider the accompanying linguistic arrangement of the articles content, and particularly, the articles title, since it is this that will firstly seduce the reader, drawing him into the commentary. The heading ‘the genetic reasons why some men are just born to cheat’ is a somewhat misleading one. Key words, such as ‘genetic’ are de-contextualised and are carelessly linked with words related to cheating and the notion of infidelity. In fact, the central study (Walum, Westberh, Henningsson, Reiss, Igl, Ganiban, Spotts, Pedersen, Eriksson & Lichtenstein, 2008) that is referred to in this article and what underpins the very foundation of the commentary, does not deal with infidelity, but rather marital quality, dissatisfaction and crisis.

The Henderson article goes on to make a number of claims and suggests that man’s tendency to be unfaithful may be influenced by his genes, the basic unit of heredity transmission from one generation to the next. Further to this, those men who inherit a specific genetic variant 334, which may affect the hormone receptor for vasopressin are more likely to have weaker relationships, and marital problems than men who do not. This claim is not as unrealistic as one might expect, since a wealth of previous empirical research has identified different genes that influence a social behaviours in a number of species, including flies (Greenspan & Ferveur, 2000), mice (Pfaff, 1999), birds (Clayton, 2000b), fish (Hofmann & Fernald, 2000), ants (Krieger & Ross, 2002), and bees (Robinson, 2002b) as well as humans. Perhaps more relevant the current discussion is a study of 1600 pairs of female twins carried out by the Twin Studies Research Unit at St Thomas’ Hospital, London. It revealed that genetic factors have a significant impact on how likely women are to cheat on their partners and how many sexual partners they are likely to have (Cherkas, Oelsner, Mak, Valdes & Spector, 2002). Findings such as these undoubtedly lend weight to Henderson’s assertions which he courageously expresses in the article without any real explanation of the scientific implications.

To clarify, genes do not specify behaviour directly, but instead encode molecular products that build and govern the functioning of the brain through which behaviour is expressed. Brain development, brain activity and behaviour all depend on both inherited and environmental influences and research suggests that social information can alter brain gene expression and behaviour (Shanahan & Hofer, 2005). Furthermore, all tissues and organs in the body consist of cells. The specialised functions of cells and how they interact determine the functions of those organs. One particular cell, the nerve cell consists of several common parts, such as the soma, dendrites and axon. It is within the neuronal membrane of these cells, inside a centrally located spherical nucleus where chromosomes, which contain the genetic material deoxyribonucleic acid (DNA), are located. Human DNA consists of 20,000 to 25,000 genes in total and it is the ‘reading’ of the DNA that is known as gene expression. The final product of gene expression is the synthesis of molecules called proteins, the building blocks of which are amino-acids.

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Henderson implicates a particular hormone called vasopressin and its receptors in his presentation of reasons for why men might commit infidelity but fails to provide any useful definition of these key terms. Vasopressin is a 9 amino-acid peptide that is synthesized principally by the magnocellular neurons of the paraventricular and supraotic nuclei in the hypothalamus, and released into the bloodstream from within the brain, from the dendrites, stomata, and axon terminals of neurosecretory neurons in the posterior pituitary gland. The gene for vasopressin is found on chromosome 20 in humans (Vincent & Fuhong, 2008) with its cell surface receptors distributed in various brain regions (Landgraf & Neumann, 2004). The peptide vasopressin, along with the similarly structured hormone, oxytocin, is released within the brain following chemical depolarization of target cells and then exerts its effect by binding to receptors. Three specific receptors for vasopressin have been identified - V1 (or AVPR1a), V2, and V3 - however the binding process occurs more rapidly for AVPR1A receptors (Vincent & Fuhong, 2008).

Henderson reports that vasopressin and AVPR1A play an important role in social behaviour, pair bonding and sexual attachment and whilst these claims can be empirically supported by a number of studies involving neuropeptide receptor mapping for example, vasopressin is best known for its effects on water regulation, body temperature, and is known to be involved with insulin release (Mutlu & Factor, 2004), and memory (Weingartner, Gold & Ballenger, 1981).

However, a large body of work firmly establishes a role for vasopressin and its receptors in social behaviours such as social recognition (Bluthe & Dantzer, 1992) communication (Goodson, 1998) aggression (Ferris, 2005), infant mother attachments and paternal care (Wang, Ferris &De Vries, 1994). It is the study of pair bonding in voles, a mouse sized rodent that is posed by Henderson as the backbone in previous research on infidelity. Pair-bonding is the monogamous relationship between sexual partners and the study of such bonds in voles provides an example of the evolution of social behaviour associated with changes in gene regulation that influence patterns of gene expression (Insel & Young, 2000). By using a partner preference test, Getz and Carter (1996) found that prairie voles, that tend to live in pairs, are monogamous and show well-established behavioural preferences for their familiar partner (Williams, Catania & Carter, 1992) in contrast to their close cousin, the meadow vole, a highly promiscuous species of vole. Henderson reports that male prairie vole’s brains contain higher levels of vasopressin than meadow voles. Whilst this claim is supported (Carter & Getz, 1993) it is the development of specific agonists and antagonists for oxytocin and vasopressin receptors that have allowed for a better understanding of the specific contributions to physiology and behaviour that each peptide makes. Pharmalogical studies as well as gene knock outs and transgenic animal studies, which involve the deliberate introduction of external or foreign DNA into the genome of an animal, have directly implicated oxytocin and vasopressin in the regulation of social behaviours. For example, a vasopressin antagonist administered to usually monogamous male prairie voles was found to block the development of partner preference and its associated aggression. Presumably, the vasopressin antagonist prevents the binding of the vasopressin and its receptor AVPR1A and therefore blocks the behavioural consequences of mating. Henderson’s reporting of another study in which ‘scientists enhanced the gene for the vasopressin receptor in meadow voles’, transforming them from promiscuous rodents to ‘loyal and attentive spouses’ further suggests that vasopressin levels are implicated in pair bonding behaviours.

An important question that Henderson raises in his article, and rightly so, is to what extents can these findings be applied to human populations? Can vasopressin and its receptors be implicated in the same way as they are in voles? Henderson cites a recent study by Walum et al (2008) in which 2,186 twins and their partners were tested on the three genetic variations in the human vasopressin receptor. Detailed measures of marital problems, personal mental health, and relationship quality were self reported on a Partner Bonding Scale (PBS) and DNA was extracted from each participant via a ‘mouth wash’. DNA was then analysed and heritability of the genetic variant was identified. One of the most common alleles (named 334), that is, one of a number of variants of the gene in question, was found to be associated with perceived partner bonding in men as assessed in the PBS. Furthermore, a correlation was found between AVPR1a receptor and human pair-bonding behaviours similarly to that reported in voles. It seems that Henderson’s initially reporting, that men who inherit the genetic variant 334 are indeed less likely to be married, less likely to form long lasting bonds and experience marital problems was correct. Although these results are in line with previous observations, their reliability however might be drawn into question if one looks closely at the methods employed in the study. Participants were asked to self report on the state of affairs in their relationship via a questionnaire and so objectivity was virtually impossible. In order for more reliable results, measures of pair-bonding that are more objective than self report would be required, for example proneness to living alone versus cohabiting, marriage and divorce.

Much remains unknown regarding the aetiology of human sexual infidelity. Such variability in results suggests that cultural and social factors can also exert a major influence on promiscuous behaviours in men. Although the Henderson article states that it would be ‘impossible to predict whether any individual would be unfaithful or a bad partner on the basis of genes’ alone, it does not however, consider the other possible contributory factors involved with infidelity. Gender alone, for instance appears to be strongly correlated with infidelity. Some authors assert that many more men compared with women engage if infidelity (Alien & Baucom, 2004), have significantly more sexual partners outside of the primary relationship (Spanier & Margolis, 1983; Wiggins & Lederer, 1984), have more permissive attitudes towards sex outside a relationship (Thomson, 1984; Lieberman, 1988) and possess a much stronger desire to engage in infidelity. Choi (1994) however found that men were only marginally more likely than women to engage in acts of infidelity and according to Oliver and Hyde (1993) men and women’s rates of infidelity are becoming increasingly similar. Perhaps more importantly, gender also appears to be related to different types of infidelity and the meanings attached to the behaviour. For example, women place greater emphasis on emotional connection, whereas men place more emphasis on the sexual experience (Glass & Wright, 1992).

Furthermore, research suggests that marriage deters men from engaging in infidelity. Treas and Giesen (2000) report that married men are less likely to engage in infidelity than those who cohabit. Atkins et al (2001) found that as marital happiness or satisfaction decreases, instances of extramarital sex increase whilst Forste & Tanfer (1996) report that the religious behaviour of an individual may have an effect on the likelihood of engaging in infidelity. In support of this view, Amato & Rogers (1997) discovered that attendance at religious services was associated with lower rates of infidelity.

Interestingly and with respect to culture, Widmer (1998) sampled over 33,000 individuals from 24 countries and found strong disapproval of extra marital relationships, although several countries including Russia, Bulgaria and Czech Republic appeared to have more tolerant views than others. Furthermore, Solstad & Music (1999) attribute the permissive attitudes of Danish men to the ‘over liberal values’ of Danish society. Atkins et al (2001) concluded that highly educated individuals, more specifically those with degrees, are more likely to have had extra marital sexual encounters than those with less than a high school education. This study also proposed that income and extramarital sexual encounters are positively correlated. Although they suggest that it might not be the money per se that leads to infidelity, but rather factors such as stress levels, education, entitlement and opportunity. Also, the risks of engaging in infidelity might be too great for those individuals who are financially dependent on their partners. Additionally, when partners are both unemployed, the incidence of extramarital sex is lower than it is when one partner works (Atkins et al, 2001). Those with a strong interest in sex are also more likely to engage in sex outside a relationship (Liu, 2000) and prior sexual experiences are also positively associated with infidelity (Treas & Giesen, 2000).

Bandura’s Social Learning Theory may also shed light on the current discussion. The idea that humans learn and comprehend attitudes and sexual behaviours as a result of social interactions with others is not inconceivable. According to Amato & Rogers (1997) parental divorce generally increases the likelihood of their children engaging in infidelity as does parental infidelities themselves. The influence of the mass media must also be considered a contributory factor, along with popular film and television. Pornography for instance, it has been argued, portrays women as commodities or sexual objects, that simply enflame the already over-potent sexual male desire and normalize the issue of infidelity.

In conclusion, social variability’s such as these are what set us apart from the male prairie and meadow vole. The Henderson article attempts to highlight similarities between pair bonding behaviours in voles and humans but fails to recognise the complex abilities that set humans apart from other animals. The unique ability to feel, experience emotions, make decisions, verbalise our thoughts, hold conversations, our ability to think in the way we do, are among just a few. The article itself is also victim to the trappings of a society eager for sensationalism, gossip and hearsay, the title of which is a clear example. It ‘dumbs down’ fascinating scientific research for a lay public who would fail to grasp it’s key concepts, and in doing so looses it’s real meaning and substance. It is something short of a summary that on a more serious note does not quantify the impressive work of the scientists involved and the intricate and technically advanced methods they use. It fails to acknowledge the mind blowing complexity of the human nervous system, the effects of peptides across species, and it does not provide any useful definition of important key terms nor does it consider the multitude of social factors involved in human living. While animal models have achieved great insight into how neuropeptides contribute to the regulation of social behaviour, there is also an expanding body of research from human studies. Understanding the links between genes and behaviour is challenging but crucial and, whilst the field is still in the formative stages, its future remains a bright one.

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